(1) Field of the Invention
The invention involves control of a spa's water speed, particularly a method of controlling water pump rotational speed using variable frequency control, rather than a water restriction valve or separate motor windings, which increases overall spa efficiency, decreases audible noise, simplifying installation costs, and allowing for a single set of controls to operate several tubs which are ganged together.
(2) Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Spas have electric motors sized from 0.5 hp to 5 hp to circulate water though a closed system. One motor is usually used in smaller spas, but multiple motors can be used on larger models. Control of water flow through the system is commonly accomplished by one of two methods.
The first method is to employ a diverter valve, placing it in the water line to the spa, which restricts the water flow, stemming the force from the pump to one zone of the tub or another, or to restrict the flow in a significant fashion. This approach requires a cut in the pipe between the pump exit port to the tub, and the insertion of the valve, so water flow to the tub is diverted or severely restricted. In this approach, the motor continues to use the same amount of energy, irrespective of the work it is doing, whether the water flow is 10% of its capabilities, or 100%.
The second method is to use multi-speed motors that have at least two sets of windings. A designer of spas can use one set of windings for one speed, but by energizing the other or both windings, the motor doubles its speed, and thus the force by which it moves the water. This approach has only two speeds, and requires a motor built for the purpose of operating with only half of its windings energized. By definition this is an inefficient motor construction, and requires a motor that is more expensive than a more traditional motor with one set of windings.
The third method is to use a triode alternating current switch, or triac connected in series with the motor. A triac is a small semiconductor device, similar to a transistor, made of different layers of semiconductor materials. By controlling the voltage applying to the gate of triac, energy flowing to the motor can be reduced. As a result, motor speed can be controlled. However, this technology has a serious issue that burns or cut the motor life short. This issue is due to the fundamental nature of the motor. It has been known that efficiency of induction AC motor is a function of voltage. Therefore, when voltage drops, motor efficiency also drops. As a result, heat will be generated. The more voltage drops the more heat will be generated. Excessive heat can damage the motor coil insulation resulting in a short circuit or motor damage.
Several means of controlling the pump speed exist. For some configurations, air switches are used to actuate a switch or relay. For others, a hand-operated dial switch is used to complete electrical circuit. The struggle with these approaches leaves commercial installations at the mercy of users who often make pump settings without authorization of the establishment managers, or leave the pump in a position of full-speed operation though no individual is in the tub, wasting enormous amounts of power.
What is needed is a simple means to securely control pump speed without cutting into the piping between the pump and tub, using inexpensive one-winding motors, using a means of control that reduces noise and increases efficiency when not operating at full speed, and to control multiple motors and tubs at one time in a secure manner, such that commercial operators can set tub jet pressure remotely and without fear of their clients changing the settings.
While this document uses the word “spa” throughout, it will be understood by those skilled in the art that this invention is equally applicable to any water jet-equipped tub appliance, such as hot tubs, Jacuzzis, and whirlpools.